Today, containers such as milk and juice cartons exist that are made from sheets of flexible materials such as plastics and cardboard. Commonly, cardboard constructed cartons have gabled tops. At a top edge of the carton, side walls fold inwardly forming a V-fold which lies between front and rear sides of the container. The container is sealed along this top edge thermally or with an adhesive to form two double wall flaps. The conventional method of opening such a container is to spread apart the flaps on one side and pull open at their center to separate their double wall and thereby form a V-shaped spout.
The breachable seal of the just described container is fairly strong to prevent accidental breaching which consumers often find difficult to break open. Many times when the consumer opens such a container, tearing occurs causing damage or fraying of the spout edges. This in turn makes it difficult to pour out the contents in a well defined stream.
To avoid this problem, various types of containers have tab opening means. One example is illustrated in U.S. Pat. No. 4,883,222 which discloses a tensile force tab attached to a leading edge of a container that utilizes simple linear pulling force to break its center seal to form a pouring spout. The tab is an integral piece that is either attached to or folded within the container leading edge. As another example, U.S. Pat. No. 4,874,126 discloses a manual grasping element such as a pull ring that is secured by a cord attached to a central apex of a carton side with a reinforced adhesive strip. A consumer pulls the ring away from the central apex to open this type container.
In the just described containers the tab is a discrete structure that is attached in some manner to the carton body. If such structural bifurcation and independency could be avoided with its attendant cost of manufacture, and a method of constructing a carton with unitary tab devised, a distinctive advance could be achieved in the art. Therefore, it is to the provision of such a method that the present invention is primarily directed.